Search for autochthonous plants as accumulators and translocators in a toxic metal-polluted coal mine soil in Okaba, Nigeria

Abstract

Increasing levels of toxic metals in soil due to natural processes (weathering of minerals, volcanic eruptions, and erosion) and anthropogenic activities (industrialization, urbanization, and mining) are global problems. Coal mining activities pollute soils with toxic metals. A valuable and inexpensive appealing technology known as phytoremediation can be employed to remove and reduce the level of metal-pollution in soil. This study was conducted in a polluted coal mine soil within Okaba (Nigeria) to identify hyper accumulator, phytoextractor and photo stabilizer plants based on the following indices: bioconcentration factor (BCF), translocation factor (TF), and bioaccumulation coefficient (BAC). Both plant and soil samples were collected, prepared and digested using various acid concentrations and mixtures to achieve complete digestion. Heavy metal (As, Cd, Cr, and Cu) concentrations from the digested samples were determined for both soil and plants in and around the mine using EDX3600B X-ray Fluorescence Spectrometer. From this study, two (2) plant species each have potential for phytoextraction and phytostabilization of As from the soil. Also, Fuirena umbrellata Rottb and Selaginella myosurus were the only plants that are suitable phytostabilizers of Cd. Arising from this study also, nine (9) plants species have been identified as potential phytostabilizers of Cr. Only Hyptis Suaveolens Poit accumulated >1000mg/kg of Cu, and therefore, hyper accumulator of Cu while thirteen (13) other species are suitable for phytostabilization of Cu. This study has shown that the native plants have the potential to naturally remove toxic metals from metal-polluted soils.